Method of recovering sugar crystals from solution



pt. 3. 1940- A. LUDWIG ET AL 2,213,710

METHOD OF RECOVERING SUGAR CRYSTALS FROM SOLUTION Filed Feb. 17, 1940 Mam:

Patented Sept. 3, 1940 METHOD OF RECOVERING SUGAR CRYSTALS FROM SOLUTION August Ludwig and Calvin L. Swihart, Menominee, Mich.

Application February 17, 1940, Serial No. 319,432

2 Claims.

The invention relates to improvements in method of recovering sugar from solution and has for its primary object the provision of an improved. method of the character indicated which will result in the recovery of a maximum of white sugar crystals of high purity from such solutions with a minimum of cost. Other objects will appear hereinafter.

The invention consists in the method of procedure hereinafter described and claimed.

The invention will be best understood by reference to the accompanying drawing which is a skeleton diagrammatic view indicating sufiicient apparatus for rendering the various novel steps embodied in our novel process clear.

In carrying on the process for the recovery of sugar from sugar beets we first prepare a solution from the beet in the usual way and commonly known as thick juice. This thick juice solution is then introduced into the usual vacuum pan or vessel 1 where it is evaporated by boiling until the usual desired concentration has been obtained to form the crystal mass known as white massecuite. The white massecuite is then transferred to the white mixer 2 ready for separation in centrifugal separator 3 where the white crystals are separated and washed in the usual way and discharged through the spout i for drying and sacking as usual.

The solution resulting from this separation is known as high green and the bulk of it is transferred through the pipe 4 to the second vacuum pan 5 where it is evaporated and crystals formed for the removal of the balance of available sugar and so that the resultant solution or melasses will be of sufiiciently low purity that it is discarded with an unusually low sugar loss in molasses. The raw massecuite thus produced is concentrated to a density of 94 degrees Brix and then is transferred to the usual crystallizer 6 permitted to complete crystallization, then transferred to the raw mixer 1 ready for separation in centrifugal separator 8. Here the raw massecuite is separated into low raw or brown sugar and molasses without washing of the crystals. As stated above, the concentration of the raw massecuite has been such and no water having been used in washing to cause resolution of crystals, that the molasses resulting therefrom in separator 8 and discharging through pipe 9 is so low in purity that it can be discarded as molasses without loss of available sugar crystals, thus dispensing with any necessity for further boiling and separation. The harmful condition resulting from organic and inorganic solutions having to be returned for boiling into the raw massecuite is overcome. These impurities have a tendency to retard crystallization and limit the recovery of sugar from sugar solutions in sugar manufacture. By thus avoiding the non-sugar concentration in the raw massecuite we promote greater crystallization with larger crystal yield and retain a higher percentage of sugar crystals in separator 8 to produce a low purity molasses for discard. This constant necessary molasses. elimination results in a good raw massecuite boiling" condition, that is, one of low viscosity and giving an excellent molasses separation in separator 8 and brown sugar crystals in proper condition for mingling.

The low raw or brown sugar coming from separator 8 and discharging through spout it] passes then to the mingler M in which it is mingled and heated with a quantity of high green solution which may be drawn through the valved pipe i2 fromthe separator 3 as indicated. Due to the scrubbing action in the mingler the film of low purity molasses is removed from the face of the crystal. After this film has been removed, the brown crystals promote crystallization from the added high green and thus collect sugar crystals or grow from the high green mingling solution and. cause a lowering in purity of the high green solution present. The optimum Brix reading in the mingler is degrees and temperature is 60 degrees centigrade.

From the mingler H the mixed brown sugar and high green solution pass to a crystallizer l3 in which this crystallization is completed. When this mixture or magma passes to the centrifugal separator M where the sugar crystals are separated from the high green solution and. are Washed to a purity of 98.5. The washed crystals obtained from separator i i are white and almost free of impurities, and pass into a melting pan l5 where they are heated and melted and then returned through pipe 56 to the vacuum pan I and crystallized in conjunction with the thick juice to recover all available white sugar crystals therefrom.

The high green solution and washing solution from centrifugal separator l4 combined is called machine syrup. This machine syrup solution is returned through pipe it to the vacuum pan 5 for recovery of sugar remaining therein and is also an important step in the raw massecuite purity control. High green solution drawn from pipe 52 is approximately 77.0 purity and due to the purity lowering of the high green through the mingling system the machine syrup from separator I4 is approximately 70.0 purity. The machine syrup at 70.0 purity is comparatively .low in impurities and therefore when blended in vacuum pan 5 will produce a raw massecuite at 75.0 purity which thus contains a minimum of impurities and thereby permits proper crystallization.

ple and effective process and apparatus for carrying on the invention, these are capable of variation and modification without departing from the spirit of theinvention. We therefore do not wish to be limited'to the precise details disclosed but desire to avail ourselves of such variations and modifications as fall within the scope of the appended claims.

We claim:

1-. The method of recovering sugar crystals from thick juice which consists constitute white massecuite and forming. and separating white crystals therefrom to leave high green solution; then re-evaporating the said high green solution to proper concentration for the first evapo rating the thick juice to proper concentration to removal of the balance of available crystals and forming and separating low raw crystals therefrom; then mingling a small quantity of said high green solution with said low raw crystals and permitting said crystals to grow from said solution; then separating said low raw crystals from their mingled high green solution and washing the crystals to form machine syrup; and then returning said machine syrup directly to said original high green solution and said low raw crystals directly to said thick juice.

2. The method of recovering sugar crystals from thick juice which consists in first evaporating the thick juice to proper concentration to constitute white massecuite and forming and separating white crystals therefrom to leave high green solution; then re-evaporatingthe said high green solution to proper concentration for removal of the balance of available crystals and forming and separating low raw crystals therefrom Without washing them; then heating to about 60 centigrade and mingling a small quantity of said high green solution with said low raw crystals and permitting said crystals to grow from said solution; then separating said low raw crystals from their mingled high green solution and washing the crystals to form machine syrup; and then returning said machine syrup directly to said original high green solution and melting said low raw crystals and returning them directly to said thick juice.

AUGUST LUDWIG.

CALVIN L. SWIHART. 

